The number of people dead after a train derailed in one of Spain's worst rail disasters has reportedly risen as high as 77.

Many more are said to be critically injured and Spanish media reported emergency services were attempting to rescue several people still trapped inside carriages.

A British national was among those injured, the Foreign Office has confirmed.

Casualties were pulled from the carriages

Lines of bodies covered with blankets were seen at the side of the tracks.

The crash happened as the train carrying 218 passengers plus crew approached Santiago de Compostela, a popular pilgrimage city in the northwestern region of Galicia.

Video:Spain Train Crash Investigation

Several of the 13 carriages rolled over, with one carriage torn open and flames and smoke seen rising from the scene.

It has been described as an accident, but it will stir memories of the 2004 Madrid train bombing, which killed nearly 200 people.

One passenger, Ricardo Montesco, told Cadena Ser radio station: "It was going so quickly ... It seems that on a curve the train started to twist and the wagons piled up one on top of the other.

"A lot of people were squashed on the bottom.

"We tried to squeeze out of the bottom of the wagons to get out and we realised the train was burning ... I was in the second wagon and there was fire ... I saw corpses."

A witness told the station they heard an explosion before seeing the derailed train. Another witness told the Radio Galega station: "There are many people dead here, my God."

The train belonging to the state-owned Renfe company was travelling from Madrid to the port city of Ferrol.

It derailed on high-speed tracks at about 8.40pm local time - 7.40pm UK time - on a bend a short distance from a scheduled stop in the city.

Spain's Prime Minister Mariano Rajoy, who is due to visit the scene later, called an emergency meeting with ministers and said: "I want to express my affection and solitarity with the victims of the terrible train accident in Santiago."

The crash happened the day before the city's main festival paying tribute to St James, one of Jesus' 12 disciples. His shrine is the destination of the El Camino de Santiago pilgrimage, which has been followed by Christians since the Middle Ages.